The Bridge of Allan cave sits on the Darn Walk, not far from Dunblane.

In the book it is described as a “large airy place, with a little spring and a pool of clear water overhanging with ferns.”

RLS, who was born in 1850, visited Bridge of Alan several times with his parents during the following decade with his mother particularly a fan of the Stirlingshire spa town for its supposed health giving properties.